A low temperature chemical vapor deposition process comprising heating a substrate upon which deposition is desired to a temperature of from about 350.degree. C. to about 700.degree. C. in a chemical vapor deposition reactor at a pressure of from about 0.1 torr to atmospheric pressure, introducing into the reactor a silicon-containing feed and an oxygen containing feed, said silicon containing feed consisting essentially of one or more compounds having the general formula ##STR1## wherein: R.sub.1, R.sub.2, and R.sub.3 are hydrogen, azido or 1-6 carbon alkyl, phenyl or 7 to 10 carbon alkaryl groups, at least one of R.sub.1 and R.sub.2 being 1-6 carbon alkyl, phenyl or 7-10 carbon alkaryl and maintaining the temperature and pressure in said ranges to cause a film of silicon dioxide or silicon oxynitride to deposit on said substrate is disclosed.

It is standard practice in the manufacture of many semiconductor devices, and other devices, to provide a thin passive layer or coating of a chemically nonreactive or low reactivity material to protect the semiconductor junctions and layers from degradation by contact with oxygen, fumes in the air, moisture, etc., and from damage by contact during packaging and handling and to stabilize the electrical characteristics of the device.
The production of silicon oxide and silicon nitride coatings application to semiconductor devices and to other devices is well known, and there is considerable literature on the subject. The general principles underlying the formation of thin films are described in HANDBOOK OF THIN FILM TECHNOLOGY, Maissell, Leon I. and Glang, Reinhard, editors, McGraw Hill Book Company, New York, 1970, and the general technology for processing silicon-based semiconductor devices in described in SILICON PROCESSING FOR THE VLSI ERA, Wolf, Stanley, and Talbert, Richard N., editors, Lattice Press, Sunset Beach, Calif., 1986, which includes a discussion of thin film technology.
Silicon dioxide and silicon oxynitride are commonly used as a film-forming material to protect semiconductor devices.
Thus, the present invention relates to the manufacture of devices in which thin films of SiO.sub.2 and/or Si.sub.x O.sub.y N.sub.z are deposited on substrates. Economically, the greatest industrial application of this invention is in the manufacture of semiconductor devices; however, the discoveries of this invention are applicable to any thin film deposition of SiO.sub.2 and Si.sub.x O.sub.y N.sub.z on substrates which are capable of being heated to temperatures in the range of from about 350.degree. C. to about 700.degree. C.
The chemistry of silanes is described by Arkles, B., Peterson, W. R., Jr., KIRK-OTHMER ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY. 3rd ed. Vol 20. 887-911. Silanes, also referred to as silicon hydrides, are compounds containing a hydrogen-silicon bond. Compounds which include only silicon-carbon bonds, i.e. where all hydrogens have been replaced by alkyl, aryl or aralkyl substituents are also referred to occasionally, and herein, as silanes.
The properties of organosilanes are determined largely by the properties of the silicon atom which is larger than the carbon atom, enabling nucleophilic attack on the silicon to occur more readily than on carbon. Electrophilic attack on hydrogen bonded to silicon is also facilitated by the small steric constraints of hydrogen and the increased bond length for Si--H. In addition to the increased bond length, the Si--H bond energy is considerably lower than C--H and is reflected in the thermal stabilities of such bonds. Organohydrosilanes begin to decompose at 440.degree.-460.degree. C. through homolytic cleavage of the Si--H bond and subsequent radical formation.
Organohydrosilanes undergo a wide variety of chemical conversions. The Si--H bond of organohydrosilanes reacts with elements of most groups of the periodic system. Organosilanes, the simplest of which is methylsilane, are stable to air. The larger-chain alkylsilanes are more stable but ignite spontaneously when vaporized in oxygen under pressure. Phenyl and cyclohexylsilane can be distilled open to the atmosphere. Trialkyl- and triarylsilanes are more stable and have been distilled at as much as 325.degree. C. without decomposition.
Alkylation and arylation of organosilanes occur readily with alkyl and aryl alkalimetal compounds with good yields, especially in tetrahydrofuran and ethyl ether according to the general reaction: EQU R.sub.n SiH.sub.4-n +(4-n)R'M.fwdarw.R.sub.n SiR'.sub.4-n +(4-n)MH
where R and R' are alkyl, aryl or aralkyl and M is Li, Na, or K and n=1 to 4.
The preparation of organosilanes by the direct process was first reported in 1945. By this method, CH.sub.3 SiH(Cl).sub.2, (CH.sub.3).sub.2 SiH(Cl).sub.2, and C.sub.2 H.sub.5 SiH(Cl).sub.2 are prepared and utilized as polymers and reactive intermediates. The synthesis involves the reaction of alkyl halides, e.g., methyl and ethyl chloride, with silicon metal or silicon alloys in a fluidized bed at 250.degree.-600.degree. C. Dialkylamino-substituted silanes have also been obtained by a similar process and similar products are formed by cleavage of disilanes by dialkylamines, e.g. diethylamine cleavage yielding [(C.sub.2 H.sub.5).sub.2 N].sub.2 SiH(Cl). Organosilanes can be synthesized most conveniently in pilot, bench, and lab scale by reduction of organic-substituted halo- and alkoxysilanes with metal hydrides. The versatility of lithium aluminum hydride permits synthesis of alkyl, alkenyl, and arylsilanes. Silanes containing functional groups, such as chloro, amino, and alkoxyl in the organic substituents, can also be prepared. Organosilanes are also produced by reaction of organohalosilanes and organoalkoxysilanes with organometallic compounds. Organolithium reagents, e.g., t-butyllithium, have also produced organohydrosilanes on reaction with organochlorosilanes and tetrahalosilanes. Disproportionation reactions have also been used to prepare organosilanes. These reactions involve interaction of organosilanes with other silicon compounds containing organic, alkoxy, and halogen groups bound to silicon. Reactions are catalyzed by a variety of materials including alkali metals, alkali metal alcoholates, and Lewis acids, e.g., aluminum, zinc, iron, and boron halides. Organochlorosilanes containing Si--H disproportionate in the presence of aluminum chloride without addition of more organosilane. A wide variety of organosilanes are most commonly prepared through reaction of inorganic and organochlorosilanes with Grignard reagents. Organosilanes containing mixed organic groups can be prepared by reaction of organodihalosilanes and diorganohalosilanes or alkoxy derivatives with alkyl or aryl Grignards. Organohydrosilanes can also be prepared by addition of halosilanes and organosilanes containing multiple Si--H bonds to olefins. These reactions are catalyzed by platinum, platinum salts, peroxides, ultraviolet light, or ionizing radiation.
Azidosilanes, the characteristics and preparation thereof, have been described; see, for example, Wiberg, Int. Symp. Organosilicon Chem., Sci. Commun., pp. 232-35, 1965; Liu, Sheng-Lieh, et al., J. Chin. Chem. Soc. (Taipei), V. 17, N. 4, pp. 229-34 (1970); Wiberg, Nils, et al., J. Organometal. Chem., V. 22, N. 2, pp. 349-56 (1970).
A large variety of "thin films" are used in the fabrication of Very Large Scale Integration (VLSI) devices. These films may be thermally grown or deposited from the vapor phase. They can be metals, semiconductors, or insulators.
Thin films for use in VLSI fabrication must satisfy a large set of rigorous chemical, structural, and electrical requirements. Film composition and thickness must be strictly controlled to facilitate etching of submicron features. Very low densities of both particulate defects and film imperfections, such as pinholes, become critical for the small linewidths, high densities, and large areas necessary for VLSI. These small geometries also create highly rugged topography for overlying films to cover. Therefore, excellent adhesion, low stress, and conformal step coverage are required of a VLSI thin film, and its own surface topography should reduce or even planarize the underlying steps if possible. Finally, non-conducting thin films must have low dielectric constants to reduce parasitic capacitances exacerbated by the scaled down film thicknesses.
Although the properties of a bulk material may be well characterized, the same material in its thin film form may have properties substantially different from those of the bulk. One reason is that thin film properties are strongly influenced by surface properties, while in bulk materials this is not the case. The thin film, by its very definition has a substantially higher surface-to-volume ratio than does a bulk material. The structure of thin films, and their method of preparation also play a vital role in determining the film properties.
The formation of such films is accomplished by a large variety of techniques, but which can conceptually be divided into two groups: (1) film growth by interaction of a vapor-deposited species with the substrate; and (2) film formation by deposition without causing changes to the substrate material. The first category includes thermal oxidation and nitridation of single crystal silicon and polysilicon and the formation of silicides by direct reaction of a deposited metal and the substrate.
The second group includes another three subclasses of deposition: (a) chemical vapor deposition, or CVD, in which solid films are formed on a substrate by the chemical reaction of vapor phase chemicals that contain the required constituents; (b) physical vapor deposition, or PVD, in which the species of the thin film are physically dislodged from a source to form a vapor which is transported across a reduced pressure region to the substrate, where it condenses to form the thin film; and (c) coating of the substrate with a liquid, which is then dried to form the solid thin film. When CVD process are used to form single-crystal thin films, the process is termed epitaxy. The formation of thin films by PVD includes the processes of sputtering and evaporation.
Thin films, generally, have smaller grain size than do bulk materials. Grain size is a function of the deposition conditions and annealing temperatures. Larger grains are observed for increased film thickness, with the effect increasing with increasing substrate or deposition temperature. The initial deposition temperature plays an important role in determining the final grain size. The dependence on deposition rate is due to the fact that even if clusters have high mobility, at high deposition rate they are quickly buried under subsequent layers. For very high deposition rates, the heat of condensation can raise the substrate temperature, thereby producing increased grain size from thermal effects.
The surface roughness of films occurs as a result of the randomness of the deposition process. Real films almost always show surface roughness, even though this represents a higher energy state than that of a perfectly flat film. Depositions at high temperatures tend to show less surface roughness. This is because increased surface mobility from the higher substrate temperatures can lead to filling of the peaks and valleys. On the other hand, higher temperatures can also lead to the development of crystal facets, which may continue to grow in favored directions, leading to increased surface roughness. At low temperatures the surface roughness as measured by surface area, tends to increase with increased film thickness. Oblique deposition which results in shadowing, also increases surface roughness. Epitaxial and amorphous deposits have shown measured surface area nearly equal to the geometrical area, implying the existence of very flat films. This has been confirmed by Scanning Electron Micrography (SEM) examination of these films. Surface roughness has also been observed to increase as a result of the presence of contamination on the substrate or in the vapor phase during deposition.
The density of a thin film provides information about its physical structure. Density is usually determined by weighing the film and measuring its volume. If a film is porous from the deposition process, it generally has a lower density than bulk material.
The crystallographic structure of thin films depends on the adatom mobility and can vary from a highly disordered or amorphous-like state to a well-ordered state, e.g. epitaxial growth on a single crystal substrate. The amorphous structures are frequently observed for the deposited dielectrics such as SiO.sub.2, SiO, and Si.sub.3 N.sub.4, while most metals result in polycrystalline structure. Silicon can be either amorphous, polycrystalline, or single crystal, depending on the deposition parameters and the substrate material.
Some polycrystalline films deposit with a fiber texture or preferred orientation. This texture can be described as having a preponderance of grains with the same orientation in a direction normal to the substrate. Deposition of polycrystalline Si on SiO.sub.2 can occur in this manner. The observed fiber texture in that case has been reported as for poly-Si deposited at 600.degree.-650.degree. C.
The single crystal substrate is the dominant factor in epitaxy. Some crystal symmetry must exist between the deposit and the substrate, and the lattice parameters of each material must be close to the same value. The lattice misfit, which is the percentage difference between the lattice constant of the deposit and that of the substrate plane in contact, must be small to achieve epitaxy. The deposition temperature also plays a role in epitaxy. Elevated temperatures increase the propensity for epitaxial growth. This is engendered by several mechanisms, including: cleaner surfaces; decreased supersaturation; and increased adatom energy.
The deposition rate also plays a role in epitaxy. Lower rates tend toward epitaxy, while higher deposition rates lead to polycrystalline or amorphous deposition. Three growth regimes are observed for the deposition of Si on a clean Si substrate: (a) at low temperature and high deposition rates the deposits are amorphous; (b) at high substrate temperatures and low rate deposition they tend to be single crystal; and (c) at intermediate conditions polycrystalline films tend to form.
Nearly all films are found to be in a state of internal stress, regardless of the means by which they have been produced. The stress may be compressive or tensile. Compressively stressed films would like to expand parallel to the substrate surface, and in the extreme, films in compressive stress will buckle up on the substrate. Films in tensile stress, on the other hand, would like to contract parallel to the substrate, and may crack if their elastic limits are exceeded. In general, the stresses in thin films are in the range of 10.sup.8 -5.times.10.sup.10 dynes/cm.sup.2. Highly stressed films are generally undesirable for VLSI applications for several reasons, including: (a) they are more likely to exhibit poor adhesion; (b) they are more susceptible to corrosion; (c) brittle films, such as inorganic dielectrics, may undergo cracking in tensile stress; and (d) the resistivity of stressed metallic films is higher than that of their annealed counterparts.
The intrinsic stress reflects the film structure in ways not yet completely understood. It has been observed that the intrinsic stress in a film depends on thickness, deposition rate, deposition temperature, ambient pressure, method of film preparation, and type of substrate used, among other parameters.
At low substrate temperatures, metal films tend to exhibit tensile stress. This decreases with increasing substrate temperature, often in a linear manner, finally going through zero or even becoming compressive. The changeover to compressive stress occurs at lower temperatures for lower melting point metals.
The effect of deposition rate on film stress is ambiguous. The film stress starts out tensile, decreases as the power increases, and finally becomes compressive with further power increase.
In practice, the chemical reactions of the reactant gases leading to the formation of a solid material may take place not only on or very close to the wafer surface, a heterogeneous reaction, but also in the gas phase, a homogeneous is usually mass-transport limited, while at lower temperatures it is surface-reaction rate-limited. In actual processes the temperature at which the deposition condition moves from one of these growth regimes to the other is dependent on the activation energy of the reaction, and the gas flow conditions in the reactor. Thus, it is impossible to extrapolate with any certainty or accuracy date or process conditions or results from one pressure regime or temperature regime to another.
In processes that are run under reaction rate-limited conditions, the temperature of the process is an important parameter. That is, uniform deposition rates throughout a reactor require conditions that maintain a constant reaction rate. This in turn implies that a constant temperature must also exist everywhere at all wafer surfaces. On the other hand, under such conditions the rate at which reactant species arrive at the surface is not as important, since their concentration does not limit the growth rate. Thus, it is not as critical that a reactor be designed to supply an equal flux of reactants to all locations of a wafer surface. It will be seen that in low-pressure CVD (LPCVD) reactors, wafers can be stacked vertically and at very close spacing because such systems operate in a reaction rate limited mode. The reason for this is as follows:
Under the low pressure of an LPCVD reactor .about.1 torr the diffusivity of the gas species is increased by a factor of 1000 over that at atmospheric pressure, and this is only partially offset by the fact that the boundary layer, the distance across which the reactants must diffuse, increases by less than the square root of the pressure. The net effect is that there is more than an order of magnitude increase in the transport of reactants to and by-products away from the substrate surface, and the rate-limiting step is thus the surface reaction.
In deposition processes that are mass-transport limited, however, the temperature control is not nearly as critical. As mentioned earlier, the mass transport process which limits the growth rate is only weakly dependent on temperature. On the other hand, it is very important that the same concentration of reactants be present in the bulk gas regions adjacent to all locations of a wafer, as the arrival rate is directly proportional to the concentration in the bulk gas. Thus, to insure films of uniform thickness across a wafer, reactors which are operated in the mass transport limited regime must be designed so that all locations of wafer surfaces and all wafers in a run are supplied with an equal flux of reactant species. Atmospheric pressure reactors that deposit SiO.sub.2 at .about.400.degree. C. operate in the mass-transport limited regime. The most widely used APCVD reactor designs provide a uniform supply of reactants by horizontally positioning the wafers and moving them under a gas stream.
CVD systems usually contain the following components: (a) gas sources; (b) gas feed lines; (c) mass-flow controllers for metering the gases into the system; (d) a reaction chamber or reactor; (e) a method for heating the wafers onto which the film is to be deposited, and in some types of systems, for adding additional energy by other means; and (f) temperature sensors. LPCVD and PECVD systems also contain pumps for establishing the reduced pressure and exhausting the gases from the chamber.
The design and operation of CVD reactors depends on a variety of factors, and hence they can be categorized in several ways. The first distinction between reactor types is whether they are hot-wall or cold-wall reactors, and this is dependent on the method used to heat the wafers. The next criterion used to distinguish reactor types is their pressure regime of operation atmospheric pressure or reduced pressure reactors. Finally, the reduced pressure group is split into: (a) low-pressure reactors the so called low-pressure CVD, or LPCVD reactors, in which the energy input is entirely thermal; and (b) those in which energy is partially supplied by a plasma as well known as plasma-enhanced CVD, or PECVD reactors. Each of the reactor types in the two pressure regimes are further divided into sub-groups, defined by reactor configuration and method of heating. Table 1 summarizes the characteristics and applications of the various CVD reactor designs.
TABLE 1 ______________________________________ Characteristics and Applications of CVD Reactors Process Advantages Disadvantages Applications ______________________________________ APCVD Simple Reactor, Poor Step Low Low Tem- Fast Deposition, Coverage, Temperature perature Low Particle Oxides, both Temperature Contamination doped and undoped LPCVD Excellent Purity High Temper- High and Uniformity, ature, Low Temperature Conformal Step Deposition Oxides, both Coverage, Large Rate doped and Wafer Capacity undoped, Silicon Nitride, Poly-Si, W, WSi.sub.2 PECVD Low Temperature, Chemical. e.g. Low Fast Deposition, H.sub.2 and Temperature Good Step Particulate Insulators Coverage over Metals, (Nitride) ______________________________________
Low pressure chemical vapor deposition (LPCVD) in some cases is able to overcome the uniformity, step coverage, and particulate contamination limitations of early APCVD systems. By operating at medium vacuum, 30-250 Pa or 0.25-2.0 torr, and higher temperatures, 550.degree.-600.degree. C., LPCVD reactors typically deposit films in the reaction rate limited regime. At reduced pressure the diffusivity of the reactant gas molecules is sufficiently increased so that mass-transfer to the substrate no longer limits the growth rate. The surface reaction rate is very sensitive to temperature, but precise temperature control is relatively easy to achieve. The elimination of mass-transfer constraints on reactor design allows the reactor to be optimized for high wafer capacity. Low pressure operation also decreases gas phase reactions, making LPCVD films less subject to particulate contamination. LPCVD is used for depositing many types of films, including poly-Si, Si.sub.3 N.sub.4, SiO.sub.2, PSG, BPSG, and W.
The two main disadvantages of LPCVD are the relatively low deposition rates, and the relatively high operating temperatures. Attempting to increase deposition rates by increasing the reactant partial pressures, tends to initiate gas phase reactions. Attempting to operate at lower temperatures, results in unacceptably slow film deposition. One of the features of the present invention is the discovery that by using selected deposition source reagents, rather than methyl-containing reagents and the like which have been traditional, greatly increased deposition rates can be accomplished without the deleterious reactions and poor results which have plagued the industry for so many years.
LPCVD reactors are designed in two primary configurations: (a) horizontal tube reactors; and (b) vertical flow isothermal reactors.
Horizontal tube, hot wall reactors are the most widely used LPCVD reactors in VLSI processing. They are employed for depositing poly-Si, silicon nitride, and undoped and doped SiO.sub.2 films. They find such broad applicability primarily because of their superior economy, throughput, uniformity, and ability to accommodate large diameter, e.g. 150 mm wafers. Their main disadvantages are susceptibility to particulate contamination and low deposition rates.
The vertical flow isothermal LPCVD reactor further extends the distributed gas feed technique, so that each wafer receives an identical supply of fresh reactants. Wafers are again stacked side by side, but are placed in perforated-quartz cages. The cages are positioned beneath long, perforated, quartz reaction-gas injector tubes, one tube for each reactant gas. Gas flows vertically from the injector tubes, through the cage perforations, past the wafers, parallel to the wafer surface and into exhaust slots below the cage. The size, number, and location of cage perforations are used to control the flow of reactant gases to the wafer surfaces. By properly optimizing cage perforation design, each wafer can be supplied with identical quantities of fresh reactants from the vertically adjacent injector tubes. Thus, this design can avoid the wafer-to-wafer reactant depletion effects of the end-feed tube reactors, requires no temperature ramping, produces highly uniform depositions, and reportedly achieves low particulate contamination.
The third and last of the major CVD deposition methods is categorized not only by pressure regime, but also by its method of energy input. Rather than relying solely on thermal energy to initiate and sustain chemical reactions, plasma enhanced CVD, or PECVD uses an rf-induced glow discharge to transfer energy into the reactant gases, allowing the substrate to remain at a lower temperature than in APCVD or LPCVD processes. Lower substrate temperature is the major advantage of PECVD, and in fact, PECVD provides a method of depositing films on substrates that do not have the thermal stability to accept coating by other methods, the most important being the formation of silicon nitride and SiO.sub.2 over metals. In addition, PECVD can enhance the deposition rate when compared to thermal reactions alone, and produce films of unique compositions and properties. Desirable properties such as good adhesion, low pinhole density, good step coverage, adequate electrical properties, and compatibility with fine-line pattern transfer processes, have led to application of these films in VLSI.
The plasma, also referred to as a glow discharge, which is defined as a partially ionized gas containing an equal number of positive and negative charges as well as some other number of non-ionized gas particles, is generated by the application of a radio frequency field to a low pressure gas, thereby creating free electrons within the discharge region. The electrons gain sufficient energy from the electric field so that when they collide with gas molecules, gas-phase dissociation and ionization of the reactant gases, e.g. silane and nitrogen or oxygen-containing species then occurs.
The energetic particles used to strike target materials to be sputtered in VLSI sputter deposition systems are generated by glow-discharges. A glow-discharge is a self-sustaining type of plasma.
The energetic species are then adsorbed on the film surface. The radicals tend to have high sticking coefficients, and also appear to migrate easily along the surface after adsorption. These two factors can lead to excellent film conformality. Upon being adsorbed on the substrate, they are subjected to ion and electron bombardment, rearrangements, reactions with other adsorbed species, new bond formations and film formation and growth. Adatom rearrangement includes the diffusion of the adsorbed atoms onto stable sites and concurrent desorption of reaction products. Desorption rates are dependent on substrate temperature, and higher temperatures produce films with fewer entrapped by-products. Gas-phase nucleation should be avoided to reduce particulate contamination.
The fact that the radicals formed in the plasma discharge are highly reactive presents some options, as well as some problems, to the process engineer. PECVD films, in general, are not stoichiometric because the deposition reactions are so varied and complicated. Moreover, by-products and incidental species are incorporated into the resultant films, especially hydrogen, nitrogen, and oxygen, in addition to the desired products. Excessive incorporation of these contaminants may lead to outgassing and concomitant bubbling, cracking, or peeling during later thermal cycling, and to threshold shifts in MOS circuits.
A plasma process requires control and optimization of several deposition parameters besides those of an LPCVD process, including rf power density, frequency, and duty cycle. The deposition process is dependent in a very complex and interdependent way on these parameters, as well as on the usual parameters of gas composition, flow rates, temperature, and pressure. Furthermore, as with LPCVD, the PECVD method is surface reaction limited, and adequate substrate temperature control is thus necessary to ensure film thickness uniformity.
Three types of PECVD reactors are available: (1) the parallel plate type; (2) the horizontal tube type; and (3) the single wafer type. It should be noted that with one major exception, the discussion on glow discharges, rf diode sputtering, and rf generated plasmas for dry etching applies to the production of rf generated plasma in PECVD reactors.
Chemical vapor deposited (CVD) SiO.sub.2 films, and their binary and ternary silicates, find wide use in VLSI processing. These materials are used as insulation between polysilicon and metal layers, between metal layers in multilevel metal systems, as getters, as diffusion sources, as diffusion and implantation masks, as capping layers to prevent outdiffusion, and as final passivation layers. In general, the deposited oxide films must exhibit uniform thickness and composition, low particulate and chemical contamination, good adhesion to the substrate, low stress to prevent cracking, good integrity for high dielectric breakdown, conformal step coverage for multilayer systems, low pinhole density, and high throughput for manufacturing.
CVD silicon dioxide is an amorphous structure of SiO.sub.4 tetrahedra with an empirical formula SiO.sub.2. Depending on the deposition conditions, as summarized in Table 2, CVD silicon dioxide may have lower density and slightly different stoichiometry from thermal silicon dioxide, causing changes in mechanical and electrical film properties, such as index of refraction, etch rate, stress, dielectric constant and high electric-field breakdown strength. Deposition at high temperatures, or use of a separate high temperature post-deposition anneal step, referred to as densification can make the properties of CVD films approach those of thermal oxide.
TABLE 2 __________________________________________________________________________ Properties of CVD and Thermal Silicon Dioxide Films Film Type Property Thermal PECVD APCVD SiCl.sub.2 H.sub.2 + N.sub.2 O TEOS __________________________________________________________________________ Deposition 800-1200 200 450 900 700 Temp. (.degree.C.) Step Cover Conformal Good Poor Conformal Conformal age Stress (.times. 10.sup.9 3C 3C-3T 3T 3T 1C-2T dynes/cm.sup.2) Dielectric 6-10 8 10 10 3-6 Strength (10.sup.6 V/cm) Etch Rate 400 60 30 30 (.ANG./min): (100:1, H.sub.2 O:HF) __________________________________________________________________________
Deviation of the CVD silicon dioxide film's refractive index, n, from that of the thermal SiO.sub.2 value of 1.46 is often used as an indicator of film quality. A value of n greater than 1.46 indicates a silicon rich film, while smaller values indicate a low density, porous film. CVD SiO.sub.2 is deposited with or without dopants, and each type has unique properties and applications.
There are various reactions that can be used to prepare CVD SiO.sub.2. The choice of reaction is dependent on the temperature requirements of the system, as well as the equipment available for the process. The deposition variables that are important for CVD SiO.sub.2 include: temperature, pressure, reactant concentrations and their ratios, presence of dopant gases, system configuration, total gas flow, and wafer spacing. There are three temperature ranges in which SiO.sub.2 is formed by CVD, each with its own chemical reactions and reactor configurations. There are: 1) low temperature deposition, 300.degree.-450.degree. C.; 2) medium temperature deposition, 650.degree.-750.degree. C.; and 3) high temperature deposition, .about.900.degree. C.
The low temperature deposition of SiO.sub.2 utilizes a reaction of silane and oxygen to form undoped SiO.sub.2 films. The depositions are carried out in APCVD reactors, primarily of the continuous belt type, in distributed feed LPCVD reactors, or in PECVD reactors. The depletion effect precludes the use of conventional LPCVD for the SiH.sub.4 +O.sub.2 reaction. The addition of PH.sub.3 to the gas flow forms P.sub.2 O.sub.5, which is incorporated into the SiO.sub.2 film to produce a phosphosilicate glass (PSG). The reactions are given by: EQU SiH.sub.4 +O.sub.2 .fwdarw.SiO.sub.2 +2H.sub.2 EQU 4PH.sub.3 +5O.sub.2 .fwdarw.2P.sub.2 O.sub.5 +6H.sub.2
The reaction between silane and excess oxygen forms SiO.sub.2 by heterogeneous surface reaction. Homogeneous gas-phase nucleation also occurs, leading to small SiO.sub.2 particles that form a white powder on the reaction chamber walls, and which may potentially cause particulate contamination in the deposited films.
The deposition rate increases slowly with increased temperature between 310.degree. and 450.degree. C. An apparent activation energy of less than 0.4 eV has been measured which is indicative of a surface adsorption or gas phase diffusion deposition process. The deposition rate can be increased at constant temperature, up to a limit by increasing the O.sub.2 :SiH.sub.4 ratio. Continued increase in the ratio eventually results in a decrease in deposition rate, as a result of O.sub.2 being adsorbed on the substrate, thus inhibiting the SiH.sub.4 decomposition.
Silicon dioxide films deposited at low temperatures exhibit lower densities than thermal SiO.sub.2, and have an index of refraction of .about.1.44. They also exhibit substantially higher etch rates in buffered hydrofluoric acid, HF solutions that thermal SiO.sub.2. Subsequent heating of such films to temperatures between 700.degree.-1,000.degree. C. causes densification. That is, this step causes the density of the material to increase from 2.1 g/cm.sup.3 to 2.2 g/cm.sup.3, the film thickness to decrease, and the etch rate in HF to decrease.
SiO.sub.2 can also be deposited by a plasma enhanced reaction between SiH.sub.4 and N.sub.2 O, nitrous oxide or O.sub.2 at temperatures between 200.degree.-400.degree. C. ##STR2##
Nitrogen and/or hydrogen is often incorporated in PECVD SiO.sub.2. A low ratio of N.sub.2 O/SiH.sub.4 will increase the index of refraction, due to large amounts of nitrogen incorporated in the film and the formation of silicon rich films. Nearly stoichiometric, n=1.46, plasma oxide films can be achieved by reacting SiH.sub.4 and O.sub.2 mixtures. The buffered HF etch rate is a sensitive measure of the film's stoichiometry and density. Lower deposition temperatures and higher N.sub.2 O/SiH.sub.4 ratios lead to less dense films and faster etch rates. As with nitride films, PECVD oxides also contain 2-10 at % H.sub.2 in the form of Si--H, Si--O--H, and H--O--H. The hydrogen concentration is a strong function of the deposition parameters. Low deposition temperatures, high rf power, and high carrier-gas flow rates are required to prevent gas phase nucleation and its attendant particulate problems.
Plasma oxide films are generally deposited in compressive stress, with values ranging between 1.times.10.sup.8 -4.times.10.sup.9 dynes/cm.sup.2, depending on deposition temperature and rate. Dielectric strengths of 4-8.times.10.sup.6 V/cm, and dielectric constants ranging from 4-5 have been obtained. Low pinhole counts have been obtained with PECVD oxides, as have very conformal coatings. Adhesion to metal is also reported to be excellent.
In the medium temperature range, SiO.sub.2 is deposited in LPCVD reactors by decomposing tetraethosiloxane, Si(OC.sub.2 H.sub.5).sub.4, also known as tetraethyl orthosilicate, or TEOS. The deposition rate for TEOS shows an exponential increase with temperature in the range of 650.degree.-800.degree. C. with an apparent activation energy of 1.9 eV. This pronounced temperature dependence can lead to thickness control problems. The deposition rate is also dependent on the TEOS partial pressure. It is linearly dependent at low partial pressures, and tends to level off as the adsorbed TEOS saturates the surface. TEOS films generally show excellent conformality.
At high temperatures, near 900.degree. C., SiO.sub.2 is formed by an LPCVD process in which dichlorosilane and nitrous oxide are reacted. The reaction is given by: EQU SiH.sub.2 CL.sub.2 +2N.sub.2 O.fwdarw.SiO.sub.2 +2N.sub.2 +2HCl.
Such depositions produce films having excellent uniformity, and with properties close to those of thermal SiO.sub.2. High-temperature LPCVD is sometimes used to deposit SiO.sub.2 over poly-Si.
Materials can be prepared with characteristics between those of nitrides and oxides, and these are called silicon oxynitrides [SiO.sub.x N.sub.y (H.sub.z)]. They are formed by reacting SiH.sub.4 with N.sub.2 O and NH.sub.3. Properties can be tailored for improved thermal stability, low stress, and crack resistance. Such films are also less permeable to moisture and other contaminants than deposited oxides. The use of helium as a carrier gas is reported to increase the uniformity of the refractive index of the films. Silicon oxynitrides also are reported to exhibit good properties for use as low-temperature deposited insulators between Al conductors. Two-layer films of PECVD silicon oxynitride and silicon nitride have been used in multilevel interconnect planarization schemes utilizing the differential etch rates of the two materials.
Many treatises, texts and a massive volume of technical journal literature describe in more detail the background of the technology in which this invention lies; see, for example, Thomas, HANDBOOK OF TRANSISTORS, SEMICONDUCTORS, INSTRUMENTS AND MICROELECTRONICS, Prentice Hall, Englewood Cliffs, N.J. 1968 and the extensive publications of the J. C. Schumacher Company, e.g. Tetraethyl Orthosilicate (TEOS), Product Data Sheet No. 6; Tetraethyl Orthosilicate for Semiconductor High Temperature Silicon Dioxide Depositions, Product Application Note No. 8; TEOS and Liquid Dopant Sources for CVD SiO.sub.2, PSG, and BPSG, Product Application Note No. 15; Adams and Capio, The Deposition of Silicon Dioxide Films at Reduced Pressure, Technical Article Reprint No. 5.
Thus, the deposition of doped and undoped silicon oxide films is an important process in semiconductor device fabrication. The decomposition process commonly utilizes toxic and pyrophoric gases. The use of safer liquid sources is the goal of many investigators. F. S. Becker and D. Pawlik, ECS 85-2(85)380, ECS 86-8 pl48 "A New LPCVD Borophosphosilicate Glass Process Based on the Doped Deposition of TEOS-Oxide". G. Smolinsky and T. P. H. F. Wendling, JECS 132(85)950 "Measurement of the Temperature Dependent stress of Silicon Oxide Films Prepared by a Variety of CVD Methods". G. Smolinsky and R. E. Dean "LPCVD of Silicon Oxide Films in the Temperature Range of 410.degree. to 600.degree. C. from Diacetoxyditertiarybutoxysilane". F. S. Becker, D. Pawlik, H. Schaefer, and G. Staudigl, JVST B4(86)232 "Process and Film Characterization of Low Pressure TEOS-Borophosphosilicate Glass". D. S. Williams and E. A. Dein "LPCVD of Borophosphosilicate Glass from Organic Reactants". The thermal decomposition of tetraethoxysilane (TEOS) has been used for over twenty years to obtain undoped silicon dioxide films in the temperature range from 600.degree. to 800.degree. C., A. Hochberg and D. O'Meara "LPCVD of Silicon Dioxide Films from Tetraethoxysilane".
The deposition of silicon dioxide films has been disclosed in copending U.S. patent application Ser. No. 07/036,979, filed Apr. 10, 1987, to which reference is made for further background as to the state of the art, and U.S. Pat. No. 4,168,330 to Kaganowicz also discloses the use of some siloxanes in the deposition of silicon oxides by glow discharge at low temperatures.
An inherent characteristic of the glow discharge method, where the source is other than a single element, is the creation of a large number of ionized and non-ionized fragments of the source. Thus, plasma discharge operations differ very significantly from the thermal process. For example, it is well known that the thermal TEOS deposition takes place at temperatures in excess 650.degree. C., even in the absence of oxygen. A plasma TEOS film deposition, on the other hand, occurs at temperatures below 350.degree. C. in the presence of oxygen but does not produce a pure silicon dioxide. The film also contains significant amounts of hydrogen and is also contaminated with organic polymer residues. These carbonaceous impurities are only eliminated in a plasma/ozone process at temperatures around 400.degree. C. minimum in the presence of excess oxygen.
Nelson, U.S. Pat. No. 4,158,717 reviews the state of the art of producing silicon nitride films and describes the production silicon nitride films as protective and anti-reflective coatings and for masking semiconductive devices by a plasma discharge in azidotrimethylsilane, (CH.sub.3).sub.3 SiN.sub.3, pointing out that azidotrimethylsilane is easier to handle than silane.
Matsuda et al, U.S. Pat. No. 4,569,855, discloses the use of azidosilanes in a very low temperature (50.degree.-150.degree. C.) high energy light activated gas deposition process for forming silicon and doped silicon films. While reference is made to alkyl, aryl and alkoxy azidosilanes, there is no specific disclosure of the use of ethyl, propyl, or butyl azidosilanes, or to higher-carbon alkyl, aryl or alkoxy azidosilanes in the Matsuda et al patent. Since the greater part of the Matsuda et al process activation energy for decomposing the gas to form a film comes from very high energy light photons, e.g. U.V., X-ray or gamma photons, it would not be possible to predict from Matsuda et al what may result from the use of higher-carbon azidosilanes in a thermal-activation method at higher temperatures.
It has now been discovered that very high quality silicon dioxide, silicon nitride and silicon oxynitride films can be deposited at hitherto unattainable deposition rates in an LPCVD process at low temperatures using 2-carbon or greater alkyl-, aryl- and aralkylazidosilanes.

Deposition of silicon dioxide and silicon oxynitride films using azidosilane sources


A technique relates testing an application under test using (AUT) testing. The testing software creates a testcase by executing the AUT under normal usage, and normal usage is defined as operating the AUT for its intended purpose. The normal usage is not part of the testing. Creating the testcase includes capturing artifacts related to running the AUT under the normal usage, and the artifacts include an input artifact to the AUT and an output artifact resulting from executing the AUT. Also, the testcase is executed by re-executing the AUT using the input artifact previously captured in the artifacts of the testcase in order to obtain a new output artifact. The testing software verifies the new output artifact resulting from execution of the testcase by comparing the output artifact previously captured in the artifacts from executing the AUT under the normal usage to the new output artifact from executing the testcase.

The present invention relates in general to computing systems, and more specifically to testing of software on computing systems.
Software testing is an investigation conducted to provide stakeholders with information about the quality of the product or service under test. Software testing can also provide an objective, independent view of the software to allow the business to appreciate and understand the risks of software implementation. Test techniques include the process of executing a program or application with the intent of finding software bugs (errors or other defects), and to verify that the software product is fit for use.
Software testing involves the execution of a software component or system component to evaluate one or more properties of interest. In general, these properties indicate the extent to which the component or system under test meets the requirements that guided its design and development, responds correctly to all kinds of inputs, performs its functions within an acceptable time, is sufficiently usable, can be installed and run in its intended environments, and achieves the general result its stakeholders desire.

INTERNATIONAL BUSINESS MACHINES CORPORATION


A method for reducing a catecholamine secretion from a cholinergically innervated, functional chromaffin body, such as a paraganglioma or hyperplasic adrenal medulla, by direct, local administration of a neurotoxin, such as a botulinum toxin.

The present invention relates to methods for treating neoplasms. In particular the present invention relates to methods for treating catecholamine secreting neoplasms, both benign and cancerous, as well as hyperplasic chromaffin cells by local administration of a neurotoxin.
Adrenal Medulla
The adrenal or suprarenal glands are small, triangular-shaped structures located on top of the kidneys. Each adrenal gland comprises an adrenal cortex or outer portion and an adrenal medulla or inner portion. The cortex surrounds and encloses the medulla.
The adrenal cortex secrets the hormones cortisol and aldosterone. Cortisol is produced during times of stress, regulates sugar usage, and is essential for maintenance of normal blood pressure. Aldosterone is one of the main regulators of salt, potassium and water balance. If both adrenal glands are removed cortisol and aldosterone replacement therapy is mandatory.
The adrenal medulla secretes the catecholamines adrenalin (synonymously epinephrine) and noradrenalin (synonymously norepinephrine). These hormones are important for the normal regulation of a variety of bodily functions, including stress reaction, when they cause an increase in blood pressure, the pumping ability of the heart, and the level of blood sugar. Removal of the adrenal medulla results in little or no hormonal deficiency because other glands in the body can compensate. Contrarily, excessive catecholamine production can be life threatening.
In the normal adult male about 85% of total catecholamine made by the adrenal medulla is adrenaline, with remaining 15% being noradrenalin. There is about 1.6 mg of catecholamine present per gram of medulla tissue. Most of the noradrenalin found in blood and urine comes not from the adrenal medulla but from postganglionic sympathetic nerve endings. If the freshly sectioned adrenal gland is placed in fixatives that contain potassium dichromate, the medulla turns brown and this is referred to as the chromaffin reaction, so named to suggest the affinity of adrenal medulla tissue for chromium salts. Hence, cells of the adrenal medulla are often called chromaffin cells. Chromaffin cells also exists outside the adrenal medulla, but usually secrete only noradrenalin, not adrenaline
The adrenal medulla can be viewed as a sympathetic ganglion innervated by preganglionic cholinergic nerve fibers. These nerve fibers release acetylcholine which causes secretion of catecholamines (primarily adrenaline) by a process of exocytosis from the chromaffin cells of the adrenal medulla. The normal adrenal medulla is innervated by the splanchnic nerve, a preganglionic, cholinergic branch of the sympathetic nervous system. The activity of the adrenal medulla is almost entirely under such cholinergic nervous control.
Chromaffin Cell Tumors
Chromaffin cells (including the chromaffin cells of the adrenal medulla) and sympathetic ganglion cells have much in common as they are both derived from a common embryonic ancestor, the sympathagonium of the neural crest, as shown diagrammatically below. Examples of the types of neoplasms which can arise from each these cell types is shown in brackets. Each of the cell types shown can potentially secrete catecholamines.
While most chromaffin cell neoplasms occur in the adrenal medulla, ectopic and multiple location chromaffin cell tumors are known, occurring most commonly in children.
1. Paragangliomas
A paraganglia (synonymously, chromaffin body) can be found in the heart, near the aorta, in the kidney, liver, gonads, and other places and is comprised of chromaffin cells which apparently originate from neural crest cells and which have migrated to a close association with autonomic nervous system ganglion cells. A paraganglioma is a neoplasm comprised of chromaffin cells derived from a paraganglia. A carotid body paraganglioma is referred to as a carotid paraganglioma, while an adrenal medulla paraganglioma is called a pheochromocytoma or a chromaffinoma.
The carotid body is often observed as a round, reddish-brown to tan structure found in the adventitia of the common carotid artery. It can be located on the posteromedial wall of the vessel at its bifurcation and is attached by ayer""s ligament through which the feeding vessels run primarily from the external carotid. A normal carotid body measures 3-5 mm in diameter. Afferent innervation appears to be provided through the glossopharyngeal nerve (the ninth cranial nerve). The glossopharyngeal nerve supplies motor fibers to the stylopharyngeus, parasympathetic secretomotor fibers to the parotid gland and sensory fibers to inter alia the tympanic cavity, interior surface of the soft palate and tonsils). Histologically, the carotid body includes Type I (chief cells with copious cytoplasm and large round or oval nuclei. The cytoplasm contains dense core granules that apparently store and release catecholamines. The normal carotid body is responsible for detecting changes in the composition of arterial blood.
Carotid paragangliomas are rare tumors overall but are the most common form of head and neck paraganglioma. The treatment of choice for most carotid body paragangliomas is surgical excision. However, because of their location in close approximation to important vessels and nerves, there is a very real risk of morbidity(mainly cranial nerve X-XII deficits and vascular injuries) and mortality which is estimated as 3-9%. Tumor size is important because those greater than 5 cm in diameter have a markedly higher incidence of complications. Perioperative alpha and beta adrenergic blockers are given (if the carotid paraganglioma is secreting catecholamines) or less preferably angiographic embolization preoperatively. Radiotherapy, either alone or in conjunction with surgery, is a second consideration and an area of some controversy. Unfortunately, due to location and/or size, paragangliomas, including carotid paragangliomas can be inoperable.
2. Pheochromocvtomas
Pheochromocytomas occur in the adrenal medulla and cause clinical symptoms related to excess catecholamine production, including sudden high blood pressure (hypertension), headache, tachycardia, excessive sweating while at rest, the development of symptoms after suddenly rising from a bent-over position, and anxiety attacks. Abdominal imaging and 24 hour urine collection for catecholamines are usually sufficient for diagnosis. Catecholamine blockade with phenoxybenzamine and metyrosine generally ameliorates symptoms and is necessary to prevent hypertensive crisis during surgery, the current therapy of choice. Standard treatment is laparoscopic adrenalectomy, although partial adrenalectomy is often used for familial forms of pheochromocytoma. Malignant (cancerous) pheochromocytomas are rare tumors.
Pheochromocytomas have been estimated to be present in approximately 0.3% of patients undergoing evaluation for secondary causes of hypertension. Pheochromocytomas can be fatal if not diagnosed or if managed inappropriately. Autopsy series suggest that many pheochromocytomas are not clinically suspected and that the undiagnosed tumor is clearly associated with morbid consequences.
The progression of changes in the adrenal medulla can be from normal adrenal medulla to adrenal medullary hyperplasia (a generalized increase in the number of cells and size of the adrenal medulla without the specific development of a tumor) to a tumor of the adrenal medulla (pheochromocytoma).
Treatment of a pheochromocytoma is surgical removal of one or both adrenal glands. Whether it is necessary to remove both adrenal glands will depend upon the extent of the disease. Patients who have had both adrenal glands removed must take daily cortisol and aldosterone replacement. Cortisol is replaced by either hydrocortisone, cortisone or prednisone and must be taken daily. Aldosterone is replaced by oral, daily fludrocortisone (Florineftm). Increased amounts of replacement hydrocortisone or prednisone are required by such patients during periods of stress, including fever, cold, influenza, surgical procedure or anesthesia.
3. Glomus Tumors
Glomus tumors (a type of paraganglioma) are generally benign neoplasms, also arising from neuroectodermal tissues, found in various parts of the body. Glomus tumors are the most common benign tumors that arise within the temporal bone and fewer than five per cent of them become malignant and metastasize. Glomus tumors arise from glomus bodies distributed along parasympathetic nerves in the skull base, thorax and neck. There are typically three glomus bodies in each ear. The glomus bodies are usually found accompanying Jacobsen""s (CN IX) or Arnold""s (CN X) nerve or in the adventitia of the jugular bulb. However, the physical location is usually the mucosa of the promontory(glomus tympanicums), or the jugular bulb (glomus jugulare).
The incidence of glomus jugulare tumors is about 1:1,300,000 population and the most striking bit of epidemiology is the predominant incidence in females with the female:male incidence ratio being at least 4:1. Catecholamine secreting (i.e. functional) tumors occur in about 1% to 3% of cases.
Glomus tumors have the potential to secrete catecholamines, similar to the adrenal medulla which also arises from neural crest tissue and can also secrete catecholamines. The neoplastic counterpart of a glomus tumor in the adrenal gland is the pheochromocytoma, and glomus tumors have been referred to as extra-adrenal pheochromocytoma. Catecholamine secreting glomus tumors can cause arrhythmia, excessive perspiration, headache, nausea and pallor.
Glomus tumors can arise in different regions of the skull base. When confined to the middle ear space, they are termed glomus tympanicum. When arising in the region of the jugular foramen, regardless of their extent, they are termed glomus jugulare. When they arise high in the neck, extending towards the jugular foramen, they are termed glomus vagale. When they arise in the area of the carotid bifurcation, they are called carotid body tumors. Other known sites of glomus tumors include the larynx, orbit, nose, and the aortic arch.
Glomus Jugulare tumors are the most common tumors of the middle ear. These tumors tend to be very vascular and are fed by branches of the external carotid artery. The symptoms of a glomus jugulare tumor include hearing loss with pulsatile ringing in the ear, dizziness, and sometimes ear pain. The patient can have a hearing loss due possibly to blockage of the middle ear, but also there can be a loss of hearing due to nerve injury from the tumor mass. Cranial nerve palsies of the nerves which control swallowing, gagging, shoulder shrugging and tongue movement can all be part of the presentation of glomus jugulare tumors. When the tympanic membrane is examined a red/blue pulsatile mass can often be seen. Symptoms are insidious in onset. Because of the location and the vascular nature of the tumors, a most common complaint is pulsatile tinnitus. It is believed that the tinnitus is secondary to mechanical impingement on the umbo is most cases. Other common symptoms are aural fullness, and (conductive) hearing loss.
Current therapy for a catecholamine secreting glomus tumor is irradiation and/or surgical ablation, preceded by administration of alpha and beta blockers. Treatment for glomus jugulare tumors includes administration of alpha and beta blockers. X-ray therapy can be used to improve symptoms even if the mass persists. It is also possible to embolize the tumor with materials which block its blood supply, however this procedure has associated problems with causing swelling of the tumor which can compress the brain stem and cerebellum as well as releasing the catecholamines from the cells which die when they lose their blood supply. Surgery can be carried out upon small tumors appropriately located. The complications of surgery for a glomus jugulare tumor are persistent leakage of cerebrospinal fluid from the ear and also palsy of one of the cranial nerves controlling face movement, sensation or hearing.
Even though the surgery may be successful glomus jugulare tumors are somewhat problematic because they have a high recurrence rate and may require multiple operations. Surgical ablation carries the risk of morbidity due mainly to iatrogenic cranial nerve deficits and CSF leaks. Lack of cranial nerve preservation is probably the most significant objection to surgical intervention because of the associated morbidity of lower cranial nerve deficits. Radiotherapy also has serious complications, including osteoradionecrosis of the temporal bone, brain necrosis, pituitary-hypothalamic insufficiency, and secondary malignancy. Other postoperative complications include CSF leaks, aspiration syndromes, meningitis, pneumonia and wound infections
Botulinum Toxin
The anaerobic, gram positive bacterium Clostridium botulinum produces a potent polypeptide neurotoxin, botulinum toxin, which causes a neuroparalytic illness in humans and animals referred to as botulism. The spores of Clostridium botulinum are found in soil and can grow in improperly sterilized and sealed food containers of home based canneries, which are the cause of many of the cases of botulism. The effects of botulism typically appear 18 to 36 hours after eating the foodstuffs infected with a Clostridium botulinum culture or spores. The botulinum toxin can apparently pass unattenuated through the lining of the gut and attack peripheral motor neurons. Symptoms of botulinum toxin intoxication can progress from difficulty walking, swallowing, and speaking to paralysis of the respiratory muscles and death.
Botulinum toxin type A is the most lethal natural biological agent known to man. About 50 picograms of botulinum toxin (purified neurotoxin complex) type A1 is a LD50 in mice. One unit (U) of botulinum toxin is defined as the LD50 upon intraperitoneal injection into female Swiss Webster mice weighing 18-20 grams each. Seven immunologically distinct botulinum neurotoxins have been characterized, these being respectively botulinum neurotoxin serotypes A, B, C1, D, E, F and G each of which is distinguished by neutralization with type-specific antibodies. The different serotypes of botulinum toxin vary in the animal species s that they affect and in the severity and duration of the paralysis they evoke. For example, it has been determined that botulinum toxin type A is 500 times more potent, as measured by the rate of paralysis produced in the rat, than is botulinum toxin type B. Additionally, botulinum toxin type B has been determined to be non-toxic in primates at a dose of 480 U/kg which is about 12 times the primate LD50 for botulinum toxin type A. Botulinum toxin apparently binds with high affinity to cholinergic motor neurons, is translocated into the neuron and blocks the release of acetylcholine.
Botulinum toxins have been used in clinical settings for the treatment of neuromuscular disorders characterized by hyperactive skeletal muscles. Botulinum toxin type A has been approved by the U.S. Food and Drug Administration for the treatment of blepharospasm, strabismus and hemifacial spasm. Non-type A botulinum toxin serotypes apparently have a lower potency and/or a shorter duration of activity as compared to botulinum toxin type A. Clinical effects of peripheral intramuscular botulinum toxin type A are usually seen within one week of injection. The typical duration of symptomatic relief from a single intramuscular injection of botulinum toxin type A averages about three months.
Although all the botulinum toxins serotypes apparently inhibit release of the neurotransmifter acetylcholine at the neuromuscular junction, they do so by affecting different neurosecretory proteins and/or cleaving these proteins at different sites. For example, botulinum types A and E both cleave the 25 kiloDalton (kD) synaptosomal associated protein (SNAP-25), but they target different amino acid sequences within this protein. Botulinum toxin types B, D, F and G act on vesicle-associated protein (VAMP, also called synaptobrevin), with each serotype cleaving the protein at a different site. Finally, botulinum toxin type C1 has been shown to cleave both syntaxin and SNAP-25. These differences in mechanism of action may affect the relative potency and/or duration of action of the various botulinum toxin serotypes.
The molecular weight of the botulinum toxin protein molecule, for all seven of the known botulinum toxin serotypes, is about 150 kD. Interestingly, the botulinum toxins are released by Clostridial bacterium as complexes comprising the 150 kD botulinum toxin protein molecule along with associated non-toxin proteins. Thus, the botulinum toxin type A complex can be produced by Clostridial bacterium as 900 kD, 500 kD and 300 kD forms. Botulinum toxin types B and C1 is apparently produced as only a 500 kD complex. Botulinum toxin type D is produced as both 300 kD and 500 kD complexes. Finally, botulinum toxin types E and F are produced as only approximately 300 kD complexes. The complexes (i.e. molecular weight greater than about 150 kD) are believed to contain a non-toxin hemaglutinin protein and a non-toxin and non-toxic nonhemaglutinin protein. These two non-toxin proteins (which along with the botulinum toxin molecule comprise the relevant neurotoxin complex) may act to provide stability against denaturation to the botulinum toxin molecule and protection against digestive acids when toxin is ingested. Additionally, it is possible that the larger (greater than about 150 kD molecular weight) botulinum toxin complexes may result in a slower rate of diffusion of the botulinum toxin away from a site of intramuscular injection of a botulinum toxin complex.
In vitro studies have indicated that botulinum toxin inhibits potassium cation induced release of both acetylcholine and norepinephrine from primary cell cultures of brainstem tissue. Additionally, it has been reported that botulinum toxin inhibits the evoked release of both glycine and glutamate in primary cultures of spinal cord neurons and that in brain synaptosome preparations botulinum toxin inhibits the release of each of the neurotransmifters acetylcholine, dopamine, norepinephrine, CGRP and glutamate.
Botulinum toxin type A can be obtained by establishing and growing cultures of Clostridium botulinum in a fermenter and then harvesting and purifying the fermented mixture in accordance with known procedures. All the botulinum toxin serotypes are initially synthesized as inactive single chain proteins which must be cleaved or nicked by proteases to become neuroactive. The bacterial strains that make botulinum toxin serotypes A and G possess endogenous proteases and serotypes A and G can therefore be recovered from bacterial cultures in predominantly their active form. In contrast, botulinum toxin serotypes C1, D and E are synthesized by nonproteolytic strains and are therefore typically unactivated when recovered from culture. Serotypes B and F are produced by both proteolytic and nonproteolytic strains and therefore can be recovered in either the active or inactive form. However, even the proteolytic strains that produce, for example, the botulinum toxin type B serotype only cleave a portion of the toxin produced. The exact proportion of nicked to unnicked molecules depends on the length of incubation and the temperature of the culture. Therefore, a certain percentage of any preparation of, for example, the botulinum toxin type B toxin is likely to be inactive, possibly accounting for the known significantly lower potency of botulinum toxin type B as compared to botulinum toxin type A. The presence of inactive botulinum toxin molecules in a clinical preparation will contribute to the overall protein load of the preparation, which has been linked to increased antigenicity, without contributing to its clinical efficacy. Additionally, it is known that botulinum toxin type B has, upon intramuscular injection, a shorter duration of activity and is also less potent than botulinum toxin type A at the same dose level.
It has been reported that botulinum toxin type A has been used in clinical settings as follows:
(1) about 75-125 units of BOTOX(copyright) per intramuscular injection (multiple muscles) to treat cervical dystonia;
(2) 5-10 units of BOTOX(copyright) per intramuscular injection to treat glabellar lines (brow furrows) (5 units injected intramuscularly into the procerus muscle and 10 units injected intramuscularly into each corrugator supercilii muscle);
(3) about 30-80 units of BOTOX(copyright) to treat constipation by intrasphincter injection of the puborectalis muscle;
(4) about 1-5 units per muscle of intramuscularly injected BOTOX(copyright) to treat blepharospasm by injecting the lateral pre-tarsal orbicularis oculi muscle of the upper lid and the lateral pre-tarsal orbicularis oculi of the lower lid.
(5) to treat strabismus, extraocular muscles have been injected intramuscularly with between about 1-5 units of BOTOX(copyright), the amount injected varying based upon both the size of the muscle to be injected and the extent of muscle paralysis desired (i.e. amount of diopter correction desired).
(6) to treat upper limb spasticity following stroke by intramuscular injections of BOTOX(copyright) into five different upper limb flexor muscles, as follows:
(a) flexor digitorum profundus: 7.5 U to 30 U
(b) flexor digitorum sublimus: 7.5 U to 30 U
(c) flexor carpi ulnaris: 10 U to 40 U
(d) flexor carpi radialis: 15 U to 60 U
(e) biceps brachii: 50 U to 200 U. Each of the five indicated muscles has been injected at the same treatment session, so that the patient receives from 90 U to 360 U of upper limb flexor muscle BOTOX(copyright) by intramuscular injection at each treatment session.
The success of botulinum toxin type A to treat a variety of clinical conditions has led to interest in other botulinum toxin serotypes. A study of two commercially available botulinum type A preparations (BOTOX(copyright) and Dysport(copyright)) and preparations of botulinum toxins type B and F (both obtained from Wako Chemicals, Japan) has been carried out to determine local muscle weakening efficacy, safety and antigenic potential. Botulinum toxin preparations were injected into the head of the right gastrocnemius muscle (0.5 to 200.0 units/kg) and muscle weakness was assessed using the mouse digit abduction scoring assay (DAS). ED50 values were calculated from dose response curves. Additional mice were given intramuscular injections to determine LD50 doses. The therapeutic index was calculated as LD50/ED50. Separate groups of mice received hind limb injections of BOTOX(copyright) (5.0 to 10.0 units/kg) or botulinum toxin type B (50.0 to 400.0 units/kg), and were tested for muscle weakness and increased water consumption, the later being a putative model for dry mouth. Antigenic potential was assessed by monthly intramuscular injections in rabbits (1.5 or 6.5 ng/kg for botulinum toxin type B or 0.15 ng/kg for BOTOX(copyright)). Peak muscle weakness and duration were dose related for all serotypes. DAS ED50 values (units/kg) were as follows: BOTOX(copyright): 6.7, Dysport(copyright): 24.7, botulinum toxin type B: 27.0 to 244.0, botulinum toxin type F: 4.3. BOTOX(copyright) had a longer duration of action than botulinum toxin type B or botulinum toxin type F. Therapeutic index values were as follows: BOTOX(copyright): 10.5, Dysport(copyright): 6.3, botulinum toxin type B: 3.2. Water consumption was greater in mice injected with botulinum toxin type B than with BOTOX(copyright), although botulinum toxin type B was less effective at weakening muscles. After four months of injections 2 of 4 (where treated with 1.5 ng/kg) and 4 of 4 (where treated with 6.5 ng/kg) rabbits developed antibodies against botulinum toxin type B. In a separate study, 0 of 9 BOTOX(copyright) treated rabbits demonstrated antibodies against botulinum toxin type A. DAS results indicate relative peak potencies of botulinum toxin type A being equal to botulinum toxin type F, and botulinum toxin type F being greater than botulinum toxin type B. With regard to duration of effect, botulinum toxin type A was greater than botulinum toxin type B, and botulinum toxin type B duration of effect was greater than botulinum toxin type F. As shown by the therapeutic index values, the two commercial preparations of botulinum toxin type A (BOTOX(copyright) and Dysport(copyright) ) are different. The increased water consumption behavior observed following hind limb injection of botulinum toxin type B indicates that clinically significant amounts of this serotype entered the murine systemic circulation. The results also indicate that in order to achieve efficacy comparable to botulinum toxin type A, it is necessary to increase doses of the other serotypes examined. Increased dosage can comprise safety. Furthermore, in rabbits, type B was more antigenic than as BOTOX(copyright), possibly because of the higher protein load injected to achieve an effective dose of botulinum toxin type B.
Acetvlcholine
Typically only a single type of small molecule neurotransmitter is released by each type of neuron in the mammalian nervous system. The neurotransmitter acetylcholine is secreted by neurons in many areas of the brain, but specifically by the large pyramidal cells of the motor cortex, by several different neurons in the basal ganglia, by the motor neurons that innervate the skeletal muscles, by the preganglionic neurons of the autonomic nervous system (both sympathetic and parasympathetic), by the postganglionic neurons of the parasympathetic nervous system, and by some of the postganglionic neurons of the sympathetic nervous system. Essentially, only the postganglionic sympathetic nerve fibers to the sweat glands, the piloerector muscles and a few blood vessels are cholinergic and most of the postganglionic neurons of the sympathetic nervous system secrete the neurotransmitter norepinephine. In most instances acetylcholine has an excitatory effect. However, acetylcholine is known to have inhibitory effects at some of the peripheral parasympathetic nerve endings, such as inhibition of the heart by the vagus nerves.
The efferent signals of the autonomic nervous system are transmitted to the body through either the sympathetic nervous system or the parasympathetic nervous system. The preganglionic neurons of the sympathetic nervous system extend from preganglionic sympathetic neuron cell bodies located in the intermediolateral horn of the spinal cord. The preganglionic sympathetic nerve fibers, extending from the cell body, synapse with postganglionic neurons located in either a paravertebral sympathetic ganglion or in a prevertebral ganglion. Since, the preganglionic neurons of both the sympathetic and parasympathetic nervous system are cholinergic, application of acetylcholine to the ganglia will excite both sympathetic and parasympathetic postganglionic neurons.
Acetylcholine activates two types of receptors, muscarinic and nicotinic receptors. The muscarinic receptors are found in all effector cells stimulated by the postganglionic neurons of the parasympathetic nervous system, as well as in those stimulated by the postganglionic cholinergic neurons of the sympathetic nervous system. The nicotinic receptors are found in the synapses between the preganglionic and postganglionic neurons of both the sympathetic and parasympathetic. The nicotinic receptors are also present in many membranes of skeletal muscle fibers at the neuromuscular junction.
Acetylcholine is released from cholinergic neurons when small, clear, intracellular vesicles fuse with the presynaptic neuronal cell membrane. A wide variety of non-neuronal secretory cells, such as, adrenal medulla (as well as the PC12 cell line) and pancreatic islet cells release catecholamines and insulin, respectively, from large dense-core vesicles. The PC12 cell line is a clone of rat pheochromocytoma cells extensively used as a tissue culture model for studies of sympathoadrenal development. Botulinum toxin inhibits the release of both types of compounds from both types of cells in vitro, permeabilized (as by electroporation) or by direct injection of the toxin into the denervated cell. Botulinum toxin is also known to block release of the neurotransmitter glutamate from cortical synaptosomes cell cultures.
What is needed therefore is an effective, non-surgical ablation, non-radiotherapy therapeutic method for treating hyperplasic and/or neoplasmic, catecholamine secreting chromaffin cells, including paragangliomas, such as glomus tumors.
The present invention meets this need and provides an effective, non-surgical ablation, non-radiotherapy therapeutic method for treating hyperplasic and/or neoplasmic, catecholamine secreting chromaffin cells, including paragangliomas, such as glomus tumors.
The present invention includes within its scope a method for treating a functional neoplasm or functional chromaffin body by local administration of a neurotoxin to a neoplasm thereby reducing a catecholamine secretion from the neoplasm. As used herein xe2x80x9cfunctionalxe2x80x9d means secreting a catecholamine, xe2x80x9clocal administrationxe2x80x9d means direct injection of the neurotoxin into or to the local area of the neoplasm and xe2x80x9cneoplasmxe2x80x9d (or synonymously xe2x80x9ctumorxe2x80x9d) means an abnormal tissue that grows more rapidly than normal and which may be either a benign tumor or a malignant tumor, that is a cancer). Systemic routes of administration, such as oral and intravenous routes of administration, are excluded from the scope of the present invention. The functional neoplasm treated can be a paraganglioma or a glomus tumor.
The neurotoxin can be locally administered in an amount of between about 10xe2x88x923 U/kg and about 35 U/kg. More preferably, the neurotoxin can be locally administered in an amount of between about 10xe2x88x922 U/kg and about 25 U/kg. Most preferably, the neurotoxin is administered in an amount of between about 10xe2x88x922 U/kg and about 15 U/kg and in a particularly preferred embodiment of the present invention the neurotoxin is administered in an amount of between about 1 U/kg and about 10 U/kg. The neurotoxin can be a neurotoxin made by a Clostridial bacterium, such as a Clostridium botulinum, Clostridium butyricum or Clostridium beratti bacterium.
Additionally, the neurotoxin can be a modified neurotoxin, that is the neurotoxin can have at least one of its amino acids deleted, modified or replaced, as compared to a native neurotoxin. Thus, the neurotoxin can be a recombinant produced neurotoxin or a derivative or fragment thereof.
Preferably, the neurotoxin used in the present method is a botulinum toxin, such as one of the botulinum toxin serotypes A, B, C1, D, E, F or G. Most preferably, the neurotoxin is botulinum toxin type A.
A preferred method according to the present invention for treating a secretory neoplasm can have the step of local administration of a therapeutic amount of a botulinum toxin to a secretory neoplasm of a human patient, thereby reducing a secretion from the neoplasm. The secretion is a catecholamine secretion and the secretory tumor can be a functional paraganglioma. Furthermore, the functional paraganglioma can be, for example, a glomus tympanicum, a glomus jugulare, glomus vagale and a carotid body tumor.
The present invention also includes a method for improving patient function, the method comprising the step of administering a neurotoxin to a functional paraganglioma of a human patient, thereby improving patient function as determined by improvement in one or more of the factors of reduced pain, reduced time spent in bed, increased ambulation, healthier attitude and a more varied lifestyle.
A further method within the scope of the present invention for treating a secretion of a patient can have the step of administering to the patient an effective amount of a botulinum toxin in order to reduce the secretion, wherein the secretion is a catecholamine secretion. And the secretion can be an endocrine secretion from a chromaffin cell. Notably, the chromaffin cell can be a hyperplasic and/or hypertonic chromaffin cell and the secretion can be a cholinergic influenced secretion.
An additional method within the scope of the present invention can be a method for treating a cholinergic influenced, endocrine, catecholamine chromaffin cell secretion of a human patient by administering to a human patient a therapeutically effective amount of botulinum toxin type A in order to reduce the secretion.
The present invention also includes a method for treating a gland by administering to a gland a botulinum toxin thereby reducing a secretory activity of the gland, wherein the gland is a catecholamine secreting gland. The gland can be an excessively secreting gland and/or the gland can be influenced by the cholinergic nervous system. Additionally, the botulinum toxin can be administered by injection into the gland or into the local area of the gland.
Another preferred method within the scope of the present invention is a method for treating an excessively catecholamine secreting gland, the method comprising the step of injecting an excessively catecholamine secreting, cholinergic nervous system influenced gland or local gland area of a human patient with a therapeutically effective amount of botulinum toxin type A in order to reduce the excessive catecholamine secretion. The invention also includes a method for treating an endocrine disorder, the method comprising the step of administering a neurotoxin to a mammal, thereby reducing an excessive secretion of an endocrine gland. Finally, the invention encompasses a method for treating an adrenal disorder, the method comprising the step of administering a neurotoxin to an adrenal gland of a mammal, thereby reducing an excessive secretion of an adrenal gland.
The present invention is based upon the discovery that various excessively secreting chromaffin cells and chromaffin bodies can be treated in vivo with a botulinum toxin to reduce the secretory activity. The target tissue is cholinergically innervated or susceptible to high toxin dosing such that the proteolytic light chain of the toxin is internalized by a cholinergic neuron which influences the activity of a chromaffin cell and/or by the target secretory chromaffin cell.
Thus, cholinergically innervated functional paragangliomas, pheochromocytomas and glomus tumors can be treated by local administration of a neurotoxin, such as a botulinum toxin. By local administration it is meant that the neurotoxin is administered directly to, into, or to the vicinity of, the tumor or local tumor area to be treated. Local administration includes intratumor injection of a neurotoxin. Non-cancerous (benign), cancerous (malignant) hyperplasic and/or hypertonic catecholamine secreting tissues can be treated by a method within the scope of the present invention. Nodular or diffuse hyperplasia which precedes pheochromocytoma can also be treated by the present method. Hence, upon early diagnosis, botulinum injection can be used to reduce catecholamine secretion by hyperplasic, cholinergically innervated chromaffin cells.
I have discovered that a particular neurotoxin, botulinum toxin, can be used with dramatic ameliorative effect to treat a catecholamine secretory activity of paragangliomas, thereby significantly superseding current surgical and radiotherapy therapeutic oncological methods with regard to such neoplasms. Significantly, a single administration of the botulinum toxin can substantially reduces the tachycardia, headache, hypertension, and other catecholamine excess symptoms which can accompany a functional paraganglioma.
The route of administration and amount of botulinum toxin administered can vary widely according to the particular oncologic disorder being treated and various patient variables including size, weight, age, disease severity and responsiveness to therapy. Method for determining the appropriate route of administration and dosage are generally determined on a case by case basis by the attending physician. Such determinations are routine to one of ordinary skill in the art (see for example, Harrison""s Principles of Internal Medicine (1997), edited by Anthony Fauci et al., 14th edition, published by McGraw Hill). For example, to treat a tinnitus due to a middle ear glomus tumor, a solution of botulinum toxin type A complex can be endoscopically administered intramuscular directly to the tumor, thereby substantially avoiding entry of the toxin into the systemic circulation.
The specific dosage appropriate for administration is readily determined by one of ordinary skill in the art according to the factor discussed above. The dosage can also depend upon the size of the tumor to be treated or denervated, and the commercial preparation of the toxin. Additionally, the estimates for appropriate dosages in humans can be extrapolated from determinations of the amounts of botulinum required for effective denervation of other non-neoplastic tissues. Thus, the amount of botulinum A to be injected is proportional to the mass and level of activity of the neoplasm to be treated. Generally, between about 0.01 and 35 units per kg of patient weight of a botulinum toxin, such as botulinum toxin type A, can be administered to effectively accomplish a toxin induced neoplastic atrophy upon administration of the neurotoxin at or to the vicinity of the neoplasm. Less than about 0.01 U/kg of a botulinum toxin does not have a significant therapeutic effect upon a functional (i.e. catecholamine secreting) neoplasm, while more than about 35 U/kg of a botulinum toxin approaches a toxic dose the neurotoxin. Careful placement of the injection needle and a low volume of neurotoxin used prevents significant amounts of botulinum toxin from appearing systemically. A more preferred dose range to a functional paraganglioma is from about 0.01 U/kg to about 25 U/kg of a botulinum toxin, such as that formulated as BOTOX(copyright). The actual amount of U/kg of a botulinum toxin to be administered depends upon factors such as the extent (mass) and level of activity of the neoplasm to be treated and the administration route chosen. Botulinum toxin type A is a preferred botulinum toxin serotype for use in the methods of the present invention.
The main site of action of botulinum toxin is the neuromuscular junction where the toxin binds rapidly and prevents the release of acetylcholine. Thus, while it is known that the botulinum toxins have a known binding affinity for cholinergic, pre-synaptic, peripheral motor neurons, I have discovered that the botulinum toxins can also bind to and translocate into a wide variety of non-neuronal secretory cells, where the toxin then acts, in the known manner, as an endoprotease upon its respective secretory vessel-membrane docking protein. Because of the lower affinity of the botulinum toxins for secretory cells, such as chromaffin cells, the toxin is preferably injected into secretory or glandular tissues to provide a high local concentration of the toxin. Thus, the present invention is applicable to the treatment of secretory, including catecholamine secreting, chromaffin cells and tumors located throughout the body, including secretory tumors with little or no cholinergic innervation.
Preferably, a neurotoxin used to practice a method within the scope of the present invention is a botulinum toxin, such as one of the serotype A, B, C, D, E, F or G botulinum toxins. Preferably, the botulinum toxin used is botulinum toxin type A, because of its high potency in humans, ready availability, and known use for the treatment of skeletal and smooth muscle disorders when locally administered by intramuscular injection.
A route for administration of a neurotoxin according to the present disclosed invention for treating a cancer can be selected based upon criteria such as the solubility characteristics of the neurotoxin toxin chosen as well as the amount of the neurotoxin to be administered. The amount of the neurotoxin administered can vary widely according to the particular disorder being treated, its severity and other various patient variables including size, weight, age, and responsiveness to therapy. For example, the extent of the neoplasm influenced is believed to be proportional to the volume of neurotoxin injected, while the quantity of the denervation is, for most dose ranges, believed to be proportional to the concentration of neurotoxin injected. Methods for determining the appropriate route of administration and dosage are generally determined on a case by case basis by the attending physician. Such determinations are routine to one of ordinary skill in the art (see for example, Harrison""s Principles of Internal Medicine (1997), edited by Anthony Fauci et al., 14th edition, published by McGraw Hill).
The present invention includes within its scope the use of any neurotoxin which has a long duration therapeutic effect when locally applied to a functioning paraganglioma of a patient. For example, neurotoxins made by any of the species of the toxin producing Clostridium bacteria, such as Clostridium botulinum, Clostridium butyricum, and Clostridium beratti can be used or adapted for use in the methods of the present invention. Additionally, all of the botulinum serotypes A, B, C, D, E, F and G can be advantageously used in the practice of the present invention, although type A is the most preferred serotype, as explained above. Practice of the present invention can provide neoplasmic atrophy and remission for 27 months or longer in humans.
It is known that catecholamine release from permeabalized adrenal medulla cells can be inhibited by a botulinum toxin. Additionally, it is known that release of insulin from permeabalized (as by electroporation) insulin secreting cells can be inhibited by a botulinum toxin. When in vitro, the cell membranes of these non-nerve cells can be permeabalized to assist introduction of a botulinum toxin into the cell""s cytosol due to the lack of cell surface receptors for a botulinum toxin. Thus, botulinum toxin type B apparently inhibits insulin secretion by cleaving synaptobrevin present in the insulin secreting cell line HIT-15. Boyd R. S., et al The Effect of Botulinum Neurotoxin-B On Insulin Release From a Beta Cell, Mov Disord 10(3):376 (1995). It is the inventor""s contention that a botulinum toxin can block the release of any vesicle mediated exocytosis from any secretory (i.e. neuronal, glandular, secretory, chromaffin) cell type, as long as the light chain of the botulinum toxin is translocated into the intracellular medium. For example, the intracellular protein SNAP-25 is widely distributed in both neuronal and non-neuronal secretory cells and botulinum toxin type A is an endopeptidase for which the specific substrate is SNAP-25. Thus, while cholinergic neurons have a high affinity acceptor for the botulinum and tetanus toxins (and are therefore more sensitive than other neurons and other cells to the inhibition of vesicle mediated exocytosis of secretory compounds), as the toxin concentration is raised, non-cholinergic sympathetic neurons, chromaffin cells and other cell types can take up a botulinum toxin and show reduced exocytosis.
Hence, by practice of the present disclosed invention, non-cholinergic nerve fibers as well as non or poorly innervated secretory neoplasms can be treated by use of an appropriately higher concentration of a botulinum toxin to bring about therapeutic atrophy of secretory neoplasms (i.e. treatment of functional (catecholamine secreting) paragangliomas) and hyperplasic chromaffin cells.
In the normal adrenal medulla, the catecholamine secretion rate is controlled by the activity of the nerves stimulating the chromaffin cells. Contrary to the general belief that the pheochromocytomas are not innervated and that the release of catecholamines from such tumors is not under nervous control, there is evidence for cholinergic innervation of such tumors. For example, electron microscopy has demonstrated a nerve with small synaptic vesicles in contact with cells containing catecholamine vesicles. Additionally, the sudden secretion of catecholamines from a pheochromocytomas into the circulation precipitated by an emotional upset, hypotension or hyperventilation points to a nervous system influence on the secretion. Furthermore, the tilting a patient with a pheochromocytoma from a horizontal to an upright position has been shown to cause an exaggerated increase in urinary norepinephrine not seen in subjects with such a tumor and this may effect result from (a) a mechanical effect (i.e. compression of the catecholamine rich tumor) (b) reflex activation of the sympathetic system in which adrenergic system increased amounts of catecholamines may have accumulated in the nerve endings of a patient with a pheochromocytoma and/or (b) activation of existing pheochromocytoma innervation.
Furthermore, a method within the scope of the present invention can provide improved patient function. xe2x80x9cImproved patient functionxe2x80x9d can be defined as an improvement measured by factors such as a reduced pain, reduced time spent in bed, increased ambulation, healthier attitude, more varied lifestyle and/or healing permitted by normal muscle tone. Improved patient function is synonymous with an improved quality of life (QOL). QOL can be assesses using, for example, the known SF-12 or SF-36 health survey scoring procedures. SF-36 assesses a patient""s physical and mental health in the eight domains of physical functioning, role limitations due to physical problems, social functioning, bodily pain, general mental health, role limitations due to emotional problems, vitality, and general health perceptions. Scores obtained can be compared to published values available for various general and patient populations.
As set forth above, I have discovered that a surprisingly effective and long lasting therapeutic effect can be achieved by local administration of a neurotoxin to a chromaffin body of a human patient. In its most preferred embodiment, the present invention is practiced by direct injection into the neoplasm or to the local area of the neoplasm of botulinum toxin type A. It has been reported that at the neuroglandular junction, the chemical denervation effect of a botulinum toxin, such as botulinum toxin type A, has a considerably longer duration of action, i.e. 27 months vs. 3 months.
The present invention does include within its scope: (a) neurotoxin complex as well as pure neurotoxin obtained or processed by bacterial culturing, toxin extraction, concentration, preservation, freeze drying and/or reconstitution and; (b) modified or recombinant neurotoxin, that is neurotoxin that has had one or more amino acids or amino acid sequences deliberately deleted, modified or replaced by known chemical/biochemical amino acid modification procedures or by use of known host cell/recombinant vector recombinant technologies, as well as derivatives or fragments of neurotoxins so made, and includes neurotoxins with one or more attached targeting moieties for chromaffin and neoplasm cells types.
Botulinum toxins for use according to the present invention can be stored in lyophilized or vacuum dried form in containers under vacuum pressure. Prior to lyophilization the botulinum toxin can be combined with pharmaceutically acceptable excipients, stabilizers and/or carriers, such as albumin. The lyophilized or vacuum dried material can be reconstituted with saline or water.

Method for treating cancer with a neurotoxin to improve patient function